The present invention generally relates to computer systems, and more specifically, to dynamic time-domain reflectometry (TDR) analysis for field replaceable unit (FRU) isolation in a running system.
Time-domain reflectometry is a measurement technique used to determine the characteristics of electrical lines and/or circuits connected to the electrical line by observing reflected waveforms. Time-domain transmissometry (TDT) is an analogous technique that measures the transmitted (rather than reflected) impulse. Together, they provide a powerful means of analyzing electrical or optical transmission media such as coaxial cable and optical fiber. Variations of TDR exist. For example, spread-spectrum time-domain reflectometry (SSTDR) is used to detect intermittent faults in complex and high-noise systems such as aircraft wiring. Coherent optical time domain reflectometry (COTDR) is another variant, used in optical systems, in which the returned signal is mixed with a local oscillator and then filtered to reduce noise. The impedance of the discontinuity can be determined from the amplitude of the reflected signal. The distance to the reflecting impedance can also be determined from the time that a pulse takes to return.